Ion beam processing method and ion beam processing apparatus

ABSTRACT

The present invention has an objective to provide a processing method and an ion beam processing apparatus capable of inhibiting deposition of redeposited films even for fine patterns. In an embodiment of the present invention, ion beam processing is performed such that an etching amount of an ion beam incident in extending directions of pattern trenches formed on a substrate is made larger than the etching amount of the ion beam incident in other directions. This processing enables fine patterns to be processed while inhibiting redeposited films from being deposited on the bottom portions of the trenches of the fine patterns.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2013/001724, filed Mar. 14, 2013, which claims thebenefit of Japanese Patent Application No. 2012-146858 filed Jun. 29,2012. The contents of the aforementioned applications are incorporatedherein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an ion beam processing apparatus. Inparticular, the present invention relates to an ion beam etchingapparatus suitable for processing on fine patterns of a semiconductormemory or the like.

BACKGROUND ART

An ion beam etching (hereinafter, also abbreviated as IBE) technique hasbeen widely used for processing a semiconductor memory, a recordingdevice, a magnetic head, and the like (for example, Patent Document 1).The IBE technique forms plasma by inputting power to an electricdischarge unit, and then forms an ion beam by extracting ions from theplasma with application of a voltage to a grid. The ion beam is madeincident on a substrate, and mainly-physically etches a material on thesubstrate.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-218829

SUMMARY OF INVENTION

In the foregoing IBE, since a physical etching component is involved ata large proportion, etching progresses by scattering an etched materialfrom the substrate. For this reason, when the IBE is performed inaccordance with patterns formed by photolithography, the etched materialscattered is redeposited on side walls of the patterns in some cases. Toremove these redeposited films, used is a method of performing IBE witha substrate tilted to a travelling direction of the ion beam.

Meanwhile, processing for what are called next generation memories suchas MRAM and RRAM (registered trademark) is required to process very finepatterns to improve the recording density. In processing such finepatterns by IBE, an ion beam incident in a direction oblique to asubstrate hardly reaches a region around bottom portions of patterntrenches. This phenomenon is specifically explained below by usingFIG. 1. FIG. 1 illustrates a state of patterning of a film deposited ona substrate 11. An ion beam I is incident on the substrate 11 in anoblique direction to the substrate 11. If the patterning on thesubstrate 11 progresses as illustrated in FIG. 1, trenches T formedbetween elements 110 become so deep that a region around the bottomportions of the trenches T is shaded by the neighboring elements 110from the ion beam I. For this reason, redeposited films R are difficultto remove sufficiently. In addition, since the ion beam I is hardlyincident onto the bottom portions of the trenches T, the etching isdifficult.

The present invention was made in order to solve the foregoing problem,and aims at providing a processing method and an ion beam processingapparatus capable of inhibiting deposition of redeposited films even onfine patterns.

The present invention for solving the foregoing problem is a method ofprocessing a substrate mounted on a substrate holder by using an ionbeam extracted from a plasma source by a grid. According to a feature ofthe method, in performing ion beam etching on the substrate located witha tilt to the grid while rotating the substrate in an in-plane directionthereof, ion beam processing is performed such that an etching amount ofan ion beam incident from an extending direction of a pattern trenchformed on the substrate is made larger than an etching amount of an ionbeam incident from another direction.

Moreover, the invention of the present application is an ion beamapparatus including: a plasma source; a grid configured to extract anion beam from the plasma source; a substrate holder capable of mountinga substrate with a tilt to the grid, and of rotating in an in-planedirection of the substrate; a control unit configured to control arotation of the substrate on the substrate holder; and a positiondetection unit configured to detect a rotational position of thesubstrate. According to a feature of the apparatus, based on a detectionresult obtained by the position detection unit, the control unit makes arotational speed of the substrate holder lower when the grid is locatedon a side in an extending direction of a pattern trench formed on thesubstrate than otherwise.

Use of the present invention enables fine patterns to be processed whileinhibiting deposition of redeposited films on the bottom portions of thetrenches of the fine patterns, although the bottom portions have beendifficult to process by using conventional IBM with oblique incidence.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically illustrating fine patterns in aconventional IBE processing method.

FIG. 2 is a diagram illustrating an ion beam etching apparatus accordingto an embodiment of the present invention.

FIG. 3 is a diagram for explaining a configuration and a function of agrid according to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a control device according to anembodiment of the present invention.

FIG. 5 is a diagram illustrating array directions of rectangularpatterns on a substrate.

FIG. 6 is a diagram for explaining a positional relationship between agrid and a substrate and a phase of the substrate according to anembodiment of the present invention.

FIG. 7A is an explanatory diagram according to an embodiment of thepresent invention where a rotational speed of a substrate rotation iscontrolled and a substrate (substrate holder) is rotated continuously.

FIG. 7B is an explanatory diagram according to the embodiment of thepresent invention where the rotational speed of the substrate rotationis controlled and a substrate (substrate holder) is rotatedintermittently.

FIG. 8 is a diagram schematically illustrating a state where ion beamsare incident on a substrate.

FIG. 9A is a diagram schematically illustrating a photoresist on asubstrate before etching processing.

FIG. 9B is a diagram schematically illustrating an array of TMR elementsfor MRAM.

FIG. 10 is a block diagram illustrating a control device according to anembodiment of the present invention.

FIG. 11A is an explanatory diagram according to an embodiment of thepresent invention where electric power to be inputted to a plasmageneration unit is controlled and a substrate (substrate holder) isrotated continuously.

FIG. 11B is an explanatory diagram according to the embodiment of thepresent invention where the electric power to be inputted to the plasmageneration unit is controlled and a substrate (substrate holder) isrotated intermittently.

FIG. 12 is a block diagram illustrating a control device according to anembodiment of the present invention.

FIG. 13A is an explanatory diagram according to an embodiment of thepresent invention where a voltage to be applied to a grid is controlledand a substrate (substrate holder) is rotated continuously.

FIG. 13B is an explanatory diagram according to the embodiment of thepresent invention where the voltage to be applied to the grid iscontrolled and a substrate (substrate holder) is rotated intermittently.

FIG. 14 is a diagram for explaining an example of patterns formed on asubstrate to which the present invention is applicable.

FIG. 15 is a diagram for explaining examples of patterns formed onsubstrates to which the present invention is applicable.

FIG. 16A is a diagram schematically illustrating a state where an ionbeam is incident on a substrate in an embodiment of the presentinvention.

FIG. 16B is a diagram schematically illustrating a state where an ionbeam is incident on a substrate in an embodiment of the presentinvention.

FIG. 17A is a diagram for explaining a projection line of an ion beam ona substrate.

FIG. 17B is a diagram for explaining extending directions of patterntrenches on a substrate.

FIG. 17C is a diagram for explaining the extending directions of thepattern trenches on the substrate.

FIG. 18 is a diagram for explaining a relationship among a positionalrelationship between a grid and a substrate, the phase of the substrate,and the rotational speed of the substrate according to an embodiment ofthe present invention.

FIG. 19 is a diagram for explaining a relationship among a positionalrelationship between a grid and a substrate, the phase of the substrate,the rotational speed of the substrate, and a tilt angle of the substrateto the grid according to an embodiment of the present invention.

FIG. 20 is a diagram for explaining an example of patterns formed on asubstrate to which the present invention is applicable.

FIG. 21 is a diagram for explaining a relationship among a positionalrelationship between a grid and a substrate, the phase of the substrate,and a rotation pause time of the substrate according to an embodiment ofthe present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention are described inreference to the drawings. The present invention is not limited to theseembodiments but can be altered as needed without departing from thespirit of the present invention. In the drawings described below, thesame reference numerals are given to those having the same functions andduplicated explanation is omitted in some cases.

First Embodiment

FIG. 2 illustrates a schematic diagram of a plasma processing apparatus.An ion beam etching apparatus 100 includes a process space 1 and aplasma generation unit 2 as a plasma source. The process space 1 isprovided with an exhaust pump 3. The plasma generation unit 2 isprovided with a bell jar 4, a gas introduction unit 5, a RF antenna 6, amatching device 7, and an electromagnet 8, and is also provided with agrid 9 at a boundary with the process space 1.

The grid 9 includes multiple electrodes. In the present invention, thegrid 9 includes three electrodes, for example, as illustrated in FIG. 3.A first electrode 70, a second electrode 71, and a third electrode 72are provided in this order when viewed from a bell jar 4 side. Apositive voltage is applied to the first electrode and a negativevoltage is applied to the second electrode, so that ions are accelerateddue to a potential difference. The third electrode 72 is also called anearth electrode and is grounded. A potential difference between thesecond electrode 71 and the third electrode 72 is controlled, so thatthe diameter of the ion beam can be controlled within a predeterminednumeric value range by using an electrostatic lens effect. The ion beamis neutralized by a neutralizer 13. This grid 9 is preferably made of amaterial having resistance to a process gas. As the material for thegrid, molybdenum, titanium, titanium carbide or pyrolytic graphite canbe cited. Instead, the grid 9 may be obtained by forming a body from amaterial other than the above listed ones, and then by coating thesurface of the body with molybdenum, titanium or titanium carbide.

A substrate holder 10 is provided in the process space 1, and an ESCelectrode, not illustrated, is connected to the substrate holder 10. Asubstrate 11 mounted on the substrate holder 10 is electrostaticallychucked and fixed by way of the ESC electrode. As another substratefixing means, various kinds of fixing means such as a clamp support maybe used. The plasma of an etching gas can be generated in the plasmageneration unit 2 by introducing the process gas from the gasintroduction unit 5 and applying high frequency to the RF antenna 6.Then, a DC voltage is applied to the grid 9 to extract ions in theplasma generation unit 2 in the form of a beam. The ion beam is causedto bombard the substrate 11 to process the substrate 11. The extractedion beam is electrically neutralized by the neutralizer 13 and thencaused to bombard the substrate 11.

The substrate holder 10 is capable of rotating the substrate 11 in itsin-plane direction (on its own axis). The substrate holder 10 includesrotation control means for controlling a rotational speed of asubstrate, the number of rotations of the substrate, and a tilt of thesubstrate holder 10 to the grid 9, and means for detecting a rotationalposition of the substrate. In addition, the substrate holder 10 mayinclude means for detecting a rotation start position of the substrate.In the present embodiment, the substrate holder 10 is provided with aposition sensor 14 as position detection means, and is capable ofdetecting the rotational position of the substrate 11. A rotary encoderis used as the position sensor 14. As the position sensor 14, anyconfiguration can be used as long as it is capable of detecting therotational position of the rotating substrate 11 like the aforementionedrotary encoder.

Although the present embodiment employs a configuration in which thesensor such as the position sensor 14 detects the rotational position ofthe substrate 11 held by the substrate holder 10 by directly detectingthe rotational position of the substrate holder 10 or the substrate 11,any configuration may be used as long as it is capable of detecting therotational detection of the substrate 11. For example, the rotationalposition of the substrate 11 may be obtained in an indirect way such ascalculation from the rotational speed and the rotation time of thesubstrate holder 10.

The rotation start position of a substrate is obtained by detecting anorientation flat or notch of the substrate. Instead, the rotation startposition can be obtained more accurately by detecting an alignment markor a pattern array provided to the substrate. The foregoing positionsensor 14 may be used as a substrate rotation start position sensor, ordetection means for detecting the alignment mark or the pattern arraymay be provided in addition to the position sensor 14. As the detectionmeans, an atomic force microscope, an optical measuring or scanningelectron microscope, or the like may be provided on a transport path,not illustrated, or a measuring apparatus equipped with the abovemeasuring device may be provided and installed adjacent to the ion beametching apparatus 100.

The substrate 11 is held on a mount surface of the substrate holder 10while being kept horizontal. As a material for the substrate 11, asilicon wafer in a disc shape is used, for example. However, thematerial is not limited to this. The substrate holder 10 is capable oftilting to the ion beam at any angle.

FIG. 5 illustrates an example of the substrate 11 to which the presentinvention is applicable. FIG. 5 depicts part of patterns formed on thesubstrate 11 in an enlarged manner. A larger number of elements J areformed on the substrate 11. A feature of the present invention is that asubstrate mounted on the substrate holder is located with a tilt to thegrid, and that an exposure dose to an ion beam from extending directionsD of pattern trenches illustrated in FIG. 5 is made larger thanotherwise by changing the rotational speed of the substrate holder.

By using FIGS. 17A to 17C, description is provided for a comparisonbetween an etching amount of the ion beam from an extending direction Dof pattern trenches and an etching amount of the ion beam from anotherdirection.

Firstly, let us assume a line segment P obtained by projecting an ionbeam extracted by the grid 9 onto a plane containing a surface of thesubstrate 11 as illustrated in FIG. 17A. Then, as illustrated in FIG.17B, the projected line segment P is decomposed into a component in oneof the extending directions D of the pattern trenches and a component ina middle direction MD between the two directions D, and these componentsof the line segment P are compared with each other to find which of thecomponents in the direction D and the direction MD is larger. In thisway, the etching amount of the ion beam from the extending direction Dof pattern trenches and the etching amount of the ion beam from theother direction can be compared with each other.

In the present embodiment, as illustrated in FIG. 17B, the extendingdirections D of the pattern trenches are a direction from 0° to 180°, adirection from 180° to 0°, a direction from 90° to 270°, and a directionfrom 270° to 90°. Meanwhile, the directions MD, which are middledirections between two directions D, are a direction from 45° to 225°, adirection from 225° to 45°, a direction from 135° to 315°, and adirection from 315° to 135°.

A more specific example is explained by using FIG. 17C. Here, let usassume an ion beam a incident on the substrate 11 in a direction at anangle 100°, and an ion beam b incident on the substrate 11 in adirection at an angle 120°. The ion beam a forms an angle of 10° to thedirection D, and forms an angle of 35° to the direction MD. As thecomponent in the direction D and the component in the direction MD ofthe ion beam a are compared, the component in the direction D is lagerbecause cos 10°:cos 35°≈0.98:0.82

On the other hand, the ion beam b forms an angle of 30° to the directionD, and forms an angle of 15° to the direction MD. As the component inthe direction D and the component in the direction MD of the ion beam bare compared, the component in the direction MD is lager because cos30°:cos 15°≈0.87:0.97. Accordingly, it can be said that the ion beam ais an ion beam incident from the pattern-trench extending direction,whereas the ion beam b is an ion beam incident from the middledirection.

In other words, if the line segment P obtained by projecting an ion beamonto the plane containing the surface of the substrate 11 is closer toan extending direction D of pattern trenches than to a middle directionMD between the extending directions D of the pattern trenches, theetching amount is dominant in the extending direction D of the patterntrenches. Hence, if the projected line segment P for an ion beam iscloser to an extending direction D of the pattern trenches than to amiddle direction MD, it can be said that the ion beam is incident fromthe extending direction of the pattern trenches

Then, to locate the substrate 11 with a tilt to the grid 9 specificallymeans to locate the grid 9 and the substrate 11 at such positions thatthe normal to the substrate 11 at the center crosses the normal to thegrid 9 at the center at predetermined angles. More specifically, thismeans to set an angle of the substrate 11 to the grid 9 within a rangefrom 0° to 90° (exclusive of 0° and 90°), where 0° is an angle formedbetween the normal to the grid 9 at the center and the normal to thesubstrate holder 10 at the center when the grid 9 and the substrate 11are parallel to each other, and 90° is an angle formed when the normalto the substrate 11 at the center and the normal to the grid 9 at thecenter cross each other at perpendicular angles. As the angle thus set,an angle preferably used is 10° to 40° when a main purpose is to etchthe bottom portions of the pattern trenches, and is 30° to 80° when amain purpose is to remove redeposited films on the side walls of theelements or the like, or to etch the side walls.

In the present invention, the tilt angle of the substrate 11 to the grid9 is defined as 0° in the state where the grid 9 and the substrate 11are parallel to each other, as described above. Moreover, the substrate11 is symmetrical with respect to the center point in the surface of thesubstrate 11, and is rotated about the center point. For this reason,when the substrate 11 is tilted from the state at the tilt angle of 0°by a predetermined angle, the angle is equivalent in all tiltdirections. More specifically, when a certain direction is defined as +and an opposite direction is defined as − in the state where the tiltangle is 0°, a tilt at +30° is equivalent to a tilt at −30°.

Hence, the value of the angle is described as a positive value inprinciple in the specification of the present application.

Note that the normal to the grid 9 at the center is a line extendingperpendicularly from the center point of the grid having a circularshape. In general, the substrate 11 is mounted on a position where thenormal to the substrate 11 at the center crosses the normal to the grid9 at the center. When the grid 9 has a shape other than the circularshape, for example, a regular hexagonal shape or a regular octagonalshape, the center point is a center intersection point of diagonal linesconnecting opposed corners. In the case of a regular pentagonal shape ora regular heptagonal shape, the center point is an intersection point ofperpendicular lines extending from the corners to the opposed sides.Moreover, when the substrate 11 is offset from the normal to the grid 9at the center, the center point of the grid 9 is also shifted accordingto the offset amount of the substrate 11.

To put it differently, the normal to the grid 9 at the center in thepresent invention is a line segment along a traveling direction of anion beam extracted by the grid 9.

Here, needless to say, the aforementioned center points of the grid 9and the substrate 11 may vary within a very small range where suchvariations have almost no influence on the process steps on thesubstrate 11.

Exposure to the ion beam from the extending directions of the patterntrenches makes it possible to reduce influence of shadows of neighboringpatterns, and thereby to process fine patterns while removingredeposited films on the bottom portions of the pattern trenches.

Next, in reference to FIG. 4, description is provided for a controldevice 20 included in the ion beam etching apparatus 100 of the presentembodiment and configured to control the foregoing constituents. FIG. 4is a block diagram illustrating the control device in the presentembodiment.

The control device 20 in the present embodiment includes a generalcomputer and various kinds of drivers, for example. More specifically,the control device 20 includes a CUP (not illustrated) that executesvarious processing operations such as calculation, control and judgment,a ROM or HDD (not illustrated) where to store various control programsto be executed by the CPU, and the like. In addition, the control device20 includes a non-volatile memory or the like (not illustrated) such asa RAM, a flash memory or an SRAM, where to temporarily store data suchas data under a processing operation by the CPU and input data. Withthis configuration, the control device 20 executes ion beam etching inaccordance with a given program stored in the aforementioned ROM or thelike, or commands from a higher level apparatus. Various kinds ofprocess conditions such as an electric discharge time, an electricdischarge power, a grid application power, a process pressure, and therotation and the tilt of the substrate holder 10 are controlled inaccordance with the commands. Moreover, it is also possible to acquireoutput values of sensors such as a pressure gauge (not illustrated) formeasuring a pressure inside the ion beam etching apparatus 100 and theposition sensor 14 as the position detection means for detecting therotational position of the substrate, so that the ion beam etching canbe controlled according to the conditions of the apparatus.

Moreover, the control device 20 includes a holder rotation control unit21 as the rotation control means for controlling the rotational speed ofthe substrate 11 according to the rotational position detected by theposition sensor 14. The holder rotation control unit 21 includes atarget speed calculator 21 a, and a drive signal generator 21 b, and hasa function to control the rotational speed of the substrate 11 bycontrolling the rotation of a rotation unit of the substrate holder 10according to the rotational position of the substrate based on thepositional relationship between the rotational position of the substrate11 and the grid 9. The control device 20 is configured to receiveinformation on the rotational position of the substrate 11 from theposition sensor 14. When the control device 20 receives theabove-mentioned information on the rotational position, the target speedcalculator 21 a calculates a target rotational speed for the currentrotational position of the substrate 11 on the basis of a value of thecurrent rotational position outputted from the position sensor 14detecting the rotational position of the substrate 11. The calculationof the value of the target rotational speed is made possible, forexample, by storing a correspondence relationship between the rotationalposition of the substrate 11 and the target rotational speed as a map inadvance. On the basis of the target rotational speed calculated by thetarget speed calculator 21 a, the drive signal generator 21 b generatesa drive signal for adjusting the rotational speed to the targetrotational speed, and outputs the drive signal to a rotation drivemechanism 30. The control device 20 is configured to send the rotationdrive mechanism 30 the drive signal generated by the drive signalgenerator 21 b.

In the example of FIG. 4, the rotation drive mechanism 30 includes aholder rotation drive unit 31, such as a motor, configured to drive thesubstrate holder 10, and a feedback control unit 32 configured todetermine an operation value of the holder rotation drive unit 31 basedon a deviation between a target value and an actual value (rotationalposition or rotational speed) outputted from the position sensor 14. Therotation drive mechanism 30 drives the substrate holder 10 by using aservo mechanism. However, the feedback control is not an essentialconstituent of the present invention, and the motor may be any one of aDC motor and an AC motor. The rotation drive mechanism 30 rotates thesubstrate holder 10 by driving the holder rotation drive unit 31 basedon the drive signal received from the control device 20.

Next, description is provided for an operation of the ion beam etchingapparatus 100 of the present invention illustrated in FIG. 2, and an ionbeam etching method implemented by using this apparatus.

As a substrate to be processed by the ion beam etching apparatus 100according to the present embodiment, a substrate is prepared in whichrectangular patterns, for example, are formed at regular intervals in amatrix-like form with long-side and short-side ends of the patternsaligned with each other as illustrated in FIG. 5. The substrate 11 ismounted on the substrate holder 10 inside the process space 1 through asubstrate transport port 16 by not-illustrated transport means, forexample, a handling robot provided to a neighboring vacuum transportchamber. The substrate transport port 16 includes a gate valve, notillustrated, and the gate valve is configured to isolate the processspace 1 and the neighboring vacuum transport chamber from each other soas not to mix their atmospheres with each other. For the mountedsubstrate 11, the rotation start position of the substrate is detectedby using the notch or orientation flat. Instead, the rotation startposition is detected in such a way that an alignment mark provided tothe substrate 11 is read by an optical camera or the like. The rotationstart position may be detected before the substrate 11 is mounted on thesubstrate holder 10, or may be detected after the substrate 11 ismounted on the substrate holder 10. In the following ion beam etching,the control on the rotational speed of the substrate 11 according to thepositional relationship between the grid 9 and the substrate 11 isperformed based on the detection result of the rotation start positionof the substrate 11.

Subsequently, a gas for electric discharge, such as Ar, is introducedinto the inside of the plasma generation unit 2 from the gasintroduction unit 5. In the case of performing reactive ion beametching, an alcohol gas, a hydrocarbon gas, a carbon oxide gas or thelike is introduced into the inside of the plasma generation unit 2.

Thereafter, an electric discharge power supply 12 supplies highfrequency power, and the plasma generation unit 2 performs electricdischarge. Then, with application of a voltage to the grid 9, the grid 9extracts ions from the plasma generation unit 2 to form an ion beam. Theion beam extracted by the grid 9 is neutralized by the neutralizer 13 tobe electrically neutral. The neutralized ion beam is caused to bombardthe substrate 11 on the substrate holder 10 to perform ion beam etching.

When the substrate 11 is mounted on the substrate holder 10, the ESCelectrode operates to cause the substrate to be fixed with electrostaticchucking. The substrate 11 mounted on the substrate holder 10 is tiltedappropriately for a process position, for example, is tilted at 20° withrespect to the grid 9. As the tilt angle, a certain angle is determinedby taking into account pattern settings on the substrate, the processgas, the process pressure, the plasma density and the like.

After the substrate holder 10 on which the substrate 11 is mounted istilted to the grid 9, the substrate holder 10 starts to rotate in thein-plane direction of the substrate 11. The position sensor 14 detectsthe rotational position of the substrate 11, and the holder rotationcontrol unit 21 performs control according to the detected rotationalposition, thereby controlling the rotational speed of the substrate 11according to the rotational position detected by the position sensor 14.

Hereinafter, the control of the rotational speed of the substrate 11 isdescribed in more details. FIG. 6 is a diagram for explaining thepositional relationship between the grid 9 and the substrate 11 and thephase of the substrate 11 in the present embodiment. FIG. 7A is anexplanatory diagram illustrating a control map of the rotational speedof a substrate in an ion beam etching method according to the presentembodiment.

By using FIGS. 5 and 6, description is provided for the relationshipbetween the grid 9 and the rotational position of the substrate 11 inthe present embodiment. The substrate 11 is mounted on the rotatablesubstrate holder 10, and the substrate holder 10 is tilted to the grid 9during ion beam etching. Here, let us consider a state whererectangle-shaped patterns are arranged at regular intervals with thelong-side and short-side ends of the patterns aligned with each other asillustrated in FIG. 5. More specifically, assuming that vertical axeseach denote an axis parallel to a line passing through the center of thesubstrate 11 from the notch 15 of the substrate 11, the patterns arearrayed on the substrate with the long sides of the rectangle-shapedpatterns aligned with the vertical axes. Then, as illustrated in FIG. 6,the rotational phase (rotational angle) θ of the substrate is definedwith the notch 15 used as a base point. Specifically, the rotationalphase θ at which the ion beam is incident in the extending directions ofthe trenches along the long sides of the patterns is 0° on the notch 15side and 180° on the opposite side. In addition, the rotational phase θat which the ion beam is incident in the extending directions of thetrenches along the short sides of the patterns is defined as 90° and270° from the notch 15 side in the clockwise direction. The rotationstart point of the substrate, the pattern shape and the pattern arraydirections are defined herein for the sake of convenience, but are notlimited to those mentioned above.

In an example of the ion beam etching method using the apparatusaccording to the present embodiment, the rotational speed y of thesubstrate is controlled such that the rotational speed can be a sinewave with respect to the rotational phase θ of the substrate asillustrated in FIG. 7A and the following formula (1):y=A sin(4(θ−α)+B  (1)A=a·B  (2)

More specifically, the holder rotation control unit 21 as the rotationcontrol means of the present invention calculates the rotational speedas a sine function which cycles four times more than the rotationalangle θ of the substrate 11 on the basis of the above formula (1). Here,A denotes an amplitude of the rotational speed, and is a product of abase speed B and a variation rate a as presented in Formula (2). Inaddition, a denotes a phase difference. The distributions of the etchingamount and a taper angle in the surface of a substrate can be optimizedfor each ion beam incident angle by changing the variation rate a andthe phase difference α. Here, the rotational phase θ of the substratehas a range of 0°≤θ−360°.

In the example of FIG. 7A, the substrate rotational speed y relative tothe substrate rotational phase θ is presented under the settings of thebase speed B at ω₀, the variation rate a at a given numeric value of 0or more, and the phase difference α at 22.5°. In this case, the rotationfrequency (rotational speed) of the substrate becomes lowest when thenotch 15 of the substrate 11 is located at the positions at 0°, 90°,180°, and 270°.

Here, specific operations and effects produced by changing therotational speed depending on the rotational phase are described byusing FIG. 7A and FIGS. 9A and 9B.

In FIG. 9A, 41 denotes a photoresist and 42 denotes an upper electrodewhich forms the uppermost surface of a metal multilayer film to beprocessed by ion beam etching. Here, 41 is not necessarily thephotoresist, but may be anything that can function as a mask in theprocessing of ion beam etching. Here, let us consider the case where TMRelements 40 in a rectangular parallelepiped shape are formed from thestate in FIG. 9A by ion beam etching as illustrated in FIG. 9B.

Here, as illustrated in FIG. 7A, the substrate rotational speed islowered when the substrate is opposed to the grid 9 at a rotationalposition in an extending direction of the trenches along the long sidesof the patterns, i.e., at the rotational position at 0° where the notch15 is located. Thus, the ion beam is incident along the long sides ofthe patterns and sufficiently etches the trenches between the patterns.Then, the rotational speed of the substrate is lowered in the samemanner at the position where the substrate is rotated by an angle of180°. In this way, the etching evenly progresses along the long-sidedirections of the patterns down to the bottom portions of the patterntrenches. For the short-side directions of the patterns, which are theother extending directions of the pattern trenches, the rotational speedis lowered when the rotational position is at 90° and 270°, and therebythe etching can be carried out along the patterns down to the bottomportions of the trenches while inhibiting deposits. Thus, the trenchesbetween the rectangular patterns are exposed to the ion beam in the fourdirections along the trenches of the patterns. As a result, the trenchessurrounding the outer peripheries of the rectangles are etched down tothe bottom portions. In this process, if the etching amount variesbetween the long-side trenches and the short-side trenches, for example,if there is such a shape difference that the long-side trenches areshallow whereas the short-side trenches are deep, the rotational speedon the long side is further lowered to increase the incident dose of theion beam. Consequently, the depth of the trenches is made even and finepatterns can be processed uniformly in shape.

In the present embodiment, the control map illustrated in FIG. 7A may bestored in advance in a memory such as a ROM included in the controldevice 20. In the case where the control map is stored in the memory inadvance as described above, the target speed calculator 21 a can operateas follows. Specifically, when receiving the information on therotational position of the substrate 11 from the position sensor 14, thetarget speed calculator 21 a refers to the above control map which isillustrated in FIG. 7A and stored in the memory, extracts the rotationalspeed corresponding to the current rotational angle θ of the substrate11 to acquire the target rotational speed, and outputs the acquiredtarget rotational speed to the drive signal generator 21 b. Thus, whenthe substrate 11 is opposed to the grid 9 at a rotational angle θ of 0°,90°, 180°, and 270° and is exposed to the ion beam from the extendingdirections of the pattern trenches, the rotational speed of thesubstrate 11 can be controlled to become lowest. On the other hand, whenthe substrate 11 located at a rotational angle θ of 45°, 135°, 225°, and315° and is exposed to the ion beam from not-extending directions of thepattern trenches, the rotational speed of the substrate 11 can becontrolled to become highest.

The rotational speed of the substrate holder 10 may be changed in amanner other than the sine function illustrated in FIG. 7A. For example,as illustrated in FIG. 18, the rotational speed may be changed by usingtwo values indicating a first speed and a second speed which is higherthan the first speed. Specifically, the rotational speed of thesubstrate is set at the first speed when the rotational angle of thesubstrate 11 is within ranges of 0° to 22.5°, 67.5° to 112.5°, 157.5° to202.5°, 247.5° to 292.5°, and 337.5° to 360. Meanwhile, the rotationalspeed of the substrate is set at the second speed when the rotationalangle of the substrate 11 is within ranges of 22.5° to 67.5°, 112.5° to157.5°, 202.5° to 247.5°, and 292.5° to 337.5°.

Instead, the rotational speed may be changed stepwise such that therotational speed of the substrate 11 can become lowest at θ of 0°, 90°,180°, and 270°, and can become highest at θ of 45°, 135°, 225°, and315°.

As described above, what is important in the present embodiment is thatthe effects of the present invention can be obtained by locating thesubstrate 11 mounted on the substrate holder 10 with a tilt to the grid9 and by lowering the rotational speed of the substrate so that theexposure dose to the ion beam from the extending directions of thepattern trenches can be large. To make the uniformity in shapefavorable, it is preferable to set an equal rotational speed forrotational positions symmetric with respect to the substrate 11 (forexample, at 135° and 315°). FIG. 8 illustrates an example of a state ofexposure to the ion beams from the extending directions of the patterntrenches. The patterns located at the outermost periphery of the arrayedpatterns tend to be etched more than the patterns on the inner side. Tofurther improve the uniformity in pattern shape, dummy patterns may beformed at the outermost periphery of the patterns.

EXAMPLE 1

FIGS. 9A and 9B are explanatory diagrams for illustrating TMR elementswhich are to be used for MRAM and each include upper and lowerelectrodes. As illustrated in FIG. 9B, a basic layer structure of a TMRelement 40 includes an upper electrode 42, a magnetization free layer43, a tunnel barrier layer 44, a magnetization fixed layer 45, anantiferromagnetic layer 46, and a lower electrode 47. For example, themagnetization fixed layer is made of a ferromagnetic material, thetunnel barrier layer is made of a metal oxide (magnesium oxide, alumina,or the like) insulating material, and the magnetization free layer ismade of a ferromagnetic material.

The TMR element 40 is formed by the steps of: stacking the foregoingmetal films on a substrate by a deposition method such as sputtering;patterning a photoresist 41 on the stacked metal films (the uppermostlayer is the upper electrode 42, in this case) as illustrated in FIG.9A; and transferring the patterning to the metal films to therebyprocess the TMR elements by ion beam etching as illustrated in FIG. 9B.Use of the ion beam etching apparatus and the ion beam etching method ofthe present embodiment enables device isolation from densely-arrayedfine patterns of the TMR elements by inhibiting etching products frombeing redeposited on the bottom portions of the patterns.

Second Embodiment

In the first embodiment, the incident angle of the ion beam from thegrid 9 to the substrate 11 is adjusted and the rotational speed of thesubstrate holder 10 is controlled to be lowered such that the exposuredose to the ion beam from the extending directions of pattern trenchescan become large as described above. The rotation method of thesubstrate holder 10 may be either continuous rotation or intermittentpulse rotation. In the present embodiment, a mode of the intermittentpulse rotation is explained.

FIG. 7A is an explanatory diagram according to the first embodimentwhere the substrate holder 10 is rotated continuously and the rotationalspeed of the substrate holder 10 is controlled. FIG. 7B is anexplanatory diagram according to the present embodiment where thesubstrate holder 10 is rotated intermittently and a rotation pause timeof the substrate rotation is controlled.

When the substrate holder 10 is rotated continuously, the holderrotation control unit 21 generates a drive signal in accordance with theformula (1), the signal being for continuously changing the rotationalspeed of the substrate 11 (angular velocity ω) such that modulation ofthe rotational speed of the substrate 11 can take place in four cycleswhile the substrate 11 makes a rotation (in one cycle) as presented inFIG. 7A. In other words, the holder rotation control unit 21 controlsthe rotation of the substrate holder 10 such that the substrate 11 cancontinuously rotate. In FIG. 7A, f0 denotes a base dose of exposure toan ion beam from the grid 9, and ω denotes a base angular velocity.

On the other hand, when the substrate 11 (substrate holder 10) isrotated intermittently (in a clock form), the holder rotation controlunit 21 controls a rotation pause time s as illustrated in FIG. 7B. Morespecifically, the holder rotation control unit 21 controls the rotationof the substrate holder 10 such that the substrate 11 can stop rotatingat two or more predetermined rotational angles and that the rotationunit of the substrate holder 10 can rotate at a fixed angular velocity(rotational speed) at the rotational angles other than the predeterminedrotational angles, for example. Under such control, the rotational speedof the substrate 11 is controlled in such a manner as to rotate thesubstrate 11 intermittently. Incidentally, the rotational speed of therotation unit of the substrate holder 10 may be fixed as describedabove, or may be changed instead. Here, in the case where the rotationalspeed (angular velocity ω) is set on the vertical axis and a time t isset on the horizontal axis, a time period during which the angularvelocity is 0 is denoted by a “rotation pause time s”. In other words,the rotation pause time s indicates a time period when the rotation ofthe substrate holder 10 is stopped in the case where the substrateholder 10 is intermittently rotated. Here, S₀ is a base rotation pausetime.

Also in the present embodiment, essential features are to locate thesubstrate mounted on the substrate holder with a tilt to the grid 9, andto make large the exposure dose to the ion beam from the extendingdirections of the pattern trenches as in the first embodiment. Asdescribed above, the rotation pause time of the substrate is made longerwhen the grid 9 is located on the sides in the extending directions ofthe pattern trenches, thereby effects similar to those of the firstembodiment can be obtained. In the present embodiment, while thesubstrate 11 (substrate holder 10) makes one rotation, the rotationpause time is modulated sinusoidally in four cycles when the grid 9 islocated on the sides in the extending directions along the long sides ofthe patterns, and on the sides in the extending directions along theshort sides of the patterns, whereby the rotation pause time on thesides in the extending directions of the pattern trenches (at thesubstrate rotational positions at 0°, 90°, 180°, and 270°) is madelonger. On the other hand, the pause time under the condition where thegrid 9 is located on sides in not-extending directions of the patterntrenches is made shorter. Thus, the exposure dose to the ion beam fromthe extending directions of the pattern trenches is made larger than theexposure dose to the ion beam from the not-extending directions of thepattern trenches. If the etching amount varies between the trenches inthe long-side direction and the trenches in the short-side direction,for example, if there is such a shape difference that the trenches onthe long sides are shallow whereas the trenches on the short sides aredeep, the rotation pause time on the long sides is made further longerto increase the exposure dose to the ion beam. Consequently, the depthof the trenches is made even and fine patterns can be processeduniformly in shape. To make the uniformity in shape favorable, it ispreferable to set an equal time for the rotation pause time atrotational positions symmetric with respect to the substrate 11 (forexample, at 135° and 315°).

Third Embodiment

In the first and second embodiments, the description is provided for themodes where the rotational speed of the substrate holder 10 iscontrolled. Instead, in the present embodiment, trenches between finepatterns are processed with control of an incident dose of an ion beamon a substrate taken by controlling supply power to be supplied toplasma generation means from an electric discharge power supply 12.Specifically, in the ion beam etching, the exposure dose to the ion beamis related to a plasma density of plasma generated by the plasmageneration unit 2, and the plasma density of the plasma generation unit2 can be changed by changing the supply power to the plasma generationmeans. Thus, the exposure dose to the ion beam can be changed accordingto an angular phase of the substrate 11.

Also in the present embodiment, essential features are to locate thesubstrate mounted on the substrate holder with a tilt to the grid 9, andto make large the exposure dose to the ion beam from the extendingdirections of the pattern trenches as in the first embodiment.

FIG. 10 is a block diagram of a control device 20 according to thepresent embodiment. In the present embodiment, the control device 20includes a power control unit 60 as electric power control means forcontrolling power (electric power) to be supplied to the plasmageneration means according to the rotational position detected by theposition sensor 14. The power control unit 60 includes a target powercalculator 60 a and an output signal generator 60 b. The power controlunit 60 has a function to control the power (electric power) to theplasma generation means on the basis of the positional relationshipbetween the rotational position of the substrate 11 and the grid 9.

The control device 20 is configured to receive information on therotational position of the substrate holder 10 from the position sensor14. When the control device 20 receives the information on therotational position, the target power calculator 60 a calculates atarget power (target electric power) for the position, based on a valueof the current rotational position of the substrate holder 10 inputtedfrom the position sensor 14 that detects the rotational position of thesubstrate holder 10. The calculation of the value of the target power ismade possible, for example, by storing a correspondence relationshipbetween the rotational position of the substrate holder 10 and thetarget power as a map in advance into a memory or the like included inthe control device 20. Based on the target power calculated by thetarget power calculator 60 a, the output signal generator 60 b generatesan output signal for adjusting the supply power to the target power, andoutputs the output signal to the power supply 12. The control device 20is configured to send the output signal generated by the output signalgenerator 60 b to the power supply 12.

Note that, in the example of FIG. 10, the power supply 12 includes apower output unit 12 b configured to supply electric power to the plasmageneration means, and a feedback control unit 12 a configured todetermine an operation value of the power output unit 12 b based on adeviation between the target value and the actual value (rotationalposition or rotational speed) outputted from the position sensor 14.However, the feedback control is not an essential constituent of thepresent invention.

Also in the present embodiment, the rotation method of the substrateholder may be continuous rotation as in the first embodiment or may beintermittent pulse rotation as in the second embodiment.

FIG. 11A is an explanatory diagram according to the present embodimentwhere the supply power to the plasma generation means is controlled anda substrate (substrate holder) is continuously rotated. FIG. 11B is anexplanatory diagram according to the present embodiment where the supplypower to the plasma generation means is controlled and a substrate(substrate holder) is intermittently rotated. In the case of theintermittent rotation of the substrate, the control of the exposure doseto the ion beam according to the rotational angle θ may be performed bychanging the rotation pause time while the supply power to the plasmageneration means is fixed.

In the embodiment according to FIGS. 11A and 11B, the power control unit60 is able to calculate power for electric discharge according to therotational angle θ of the substrate 11 by using a sine function whichcycles four times more as in Formula (1). More specifically, the powercontrol unit 60 generates an output signal for modulating the supplypower to the plasma generation means in four cycles while the substrate11 (substrate holder 10) makes one rotation (in one cycle). In thisprocess, the supply power to the plasma generation means may be changedsmoothly and continuously, or may be changed stepwise. As illustrated inFIGS. 11A and 11B, the power control unit 60 may control the electricdischarge power supply 12 such that the power (electric power) suppliedat the rotational angles θ=0°, 90°, 180°, and 270° at which the grid 9is opposed to the sides in the extending directions of the patterntrenches can reach a maximum value to maximize the incident dose of theion beam on the substrate 11, while the power (electric power) suppliedat certain rotational angles other than the foregoing angles can reach aminimum value to minimize the incident dose of the ion beam on thesubstrate 11.

Thus, in the present embodiment, the effects of the present inventioncan be produced by locating the substrate mounted on the substrateholder with a tile to the grid 9 and by controlling the electricdischarge power supply 12 such that the supply power from the powercontrol unit 60 is increased so as to make large the exposure dose tothe ion beam from the extending directions of the pattern trenches. Inaddition, to make the uniformity in shape favorable, it is preferable toset an equal voltage for an application voltage at rotational positionssymmetric with respect to the substrate 11 (for example, at 135° and315°).

Fourth Embodiment

In the third embodiment, the description provided for the method ofimproving the uniformity of a processed surface by controlling thesupply power to the plasma generation means. In the present embodiment,trenches between fine patterns are processed while a beam extractionvoltage is being changed. In ion beam etching, after plasma is generatedin the plasma generation unit 2, a beam is formed by extracting ions inthe plasma generation unit 2 by means of a voltage applied to the grid9. In this regard, energy of the ion beam extracted from the plasmageneration unit 2 depends on the beam extraction voltage, and thereforethe trenches between the fine patterns are processed while the voltageis being changed according to the rotational phase of the substrate.

FIG. 3 illustrates an enlarged view of the grid 9 in FIG. 2. The beamextraction voltage in the present embodiment is explained by using FIG.3.

In FIG. 3, the upper side is the plasma generation unit 2, and the lowerside is the process space 1. The grid 9 includes the first electrode 70,the second electrode 71, and the third electrode 72 arranged in thisorder when viewed from the plasma generation unit 2 side. FIG. 3illustrates a state where the ions are extracted by the electrodes fromthe plasma generated in the plasma generation unit 2, and thereby theion beam is formed. A positive voltage is applied to the first electrode70 by a first electrode power supply 73. A negative voltage is appliedto the second electrode 71 by a second electrode power supply 74. Sincethe positive voltage is applied to the first electrode 70, ions areaccelerated due to a potential difference from the first electrode 70.

The third electrode 72 is also called an earth electrode and isgrounded. By controlling the potential difference between the secondelectrode 71 and the third electrode 72, an ion beam diameter of the ionbeam can be controlled within a predetermined numeric value range byusing an electrostatic lens effect.

In the present embodiment, the substrate holder and the third electrodeare usually at a grounded potential. For this reason, the ion beamenergy is determined depending on the positive voltage applied to thefirst electrode. Accordingly, in the present embodiment, the voltageapplied to the first electrode is a beam extraction voltage.Hereinafter, description is provided for an embodiment in the case wherethe beam extraction voltage is changed by changing the voltage appliedto the first electrode.

Also in the present embodiment, essential features are to locate thesubstrate 11 mounted on the substrate holder 10 with a tilt to the grid9, and to make large the exposure dose to the ion beam from theextending directions of the pattern trenches as in all the otherembodiments.

FIG. 12 is a block diagram of a control device 20 according to thepresent embodiment. In the present embodiment, the control device 20includes an application voltage control unit 80 as voltage control meansfor controlling a voltage (beam extraction voltage) to be applied to thefirst electrode 70 according to the rotational position detected by theposition sensor 14. The application voltage control unit 80 includes atarget voltage calculator 80 a and an output signal generator 80 b andhas a function to control the application voltage to the first electrode70 on the basis of the positional relationship between the rotationalphase of the substrate 11 and the grid 9.

The control device 20 is configured to receive information on therotational position of the substrate holder 10 from the position sensor14. When the control device 20 receives the information on therotational position, the target voltage calculator 80 a calculates atarget voltage for the position based on a value of the currentrotational phase of the substrate holder 10 inputted from the positionsensor 14 that detects the rotational phase of the substrate holder 10.The calculation of the value of the target voltage is made possible, forexample, by storing a correspondence relationship between the rotationalposition of the substrate holder 10 and the target voltage as a map inadvance into a memory or the like included in the control device 20.Based on the target power calculated by the target voltage calculator 80a, the output signal generator 80 b generates an output signal foradjusting the application voltage to the target voltage, and outputs theoutput signal to the first electrode power supply 73. The control device20 is configured to send the output signal generated by the outputsignal generator 80 b to the first electrode power supply 73.

Note that, in the example of FIG. 12, the first electrode power supply73 includes an application voltage output unit 73 b configured to applya voltage to the first electrode 70, and a feedback control unit 73 aconfigured to determine an operation value of the application voltageoutput unit 73 b based on a deviation between the target value and theactual value (rotational position or rotational speed) outputted fromthe position sensor 14. However, the feedback control is not anessential constituent of the present invention.

Also in the present embodiment, the rotation method of the substrateholder may be continuous rotation as in the first embodiment or may beintermittent pulse rotation as in the second embodiment.

FIG. 13A is an explanatory diagram according to the present embodimentwhere the beam extraction voltage (namely, the application voltage tothe first electrode 70) is controlled and a substrate (substrate holder)is continuously rotated. FIG. 13B is an explanatory diagram according tothe present embodiment where the application voltage to the grid 9 iscontrolled and a substrate (substrate holder) is intermittently rotated.In the case where the substrate is intermittently rotated, the controlof the exposure dose to the ion beam according to the rotational angle θmay be performed by changing the rotation pause time while theapplication voltage to the grid 9 is fixed.

In the embodiment according to FIGS. 13A and 13B, the applicationvoltage control unit 80 is able to calculate the application voltageaccording to the rotational angle θ of the substrate 11 by using a sinefunction which cycles four times more as in Formula (1). Morespecifically, the application voltage control unit 80 generates anoutput signal for modulating the beam extraction voltage in four cycleswhile the substrate 11 (substrate holder 10) makes one rotation (in onecycle). In this process, the beam extraction voltage may be changedsmoothly and continuously, or may be changed stepwise. For example, asillustrated in FIGS. 13A and 13B, the application voltage control unit80 may control the first electrode power supply 73 as follows.Specifically, the voltage applied to the first electrode 70 at therotational angle θ=0°, 90°, 180°, and 270°, at which the grid 9 islocated on the sides in the extending directions of the patterntrenches, may be controlled to reach a maximum value to maximize the ionbeam energy, and thereby to make large the incident dose of the ion beamfrom the extending directions of the pattern trenches. Meanwhile, thevoltage applied to the first electrode 70 when the grid 9 is located onthe sides in the not-extending directions of the pattern trenches may becontrolled to reach a minimum value to minimize the ion beam energy. Inthe case of minimizing the ion beam energy, the voltage to be applied tothe grid 9 may be set to zero to stop exposure of the substrate 11 tothe ion beam.

In this way, in the present embodiment, the effects of the presentinvention can be obtained by locating the substrate mounted on thesubstrate holder with a tilt to the grid 9, and by the applicationvoltage control unit 80 controlling the application voltage of the firstelectrode power supply 73 such that the exposure dose to the ion beamfrom the extending directions of the pattern trenches can be made large.To make the uniformity in shape favorable, it is preferable to set equalpower for the supply power at rotational positions symmetric withrespect to the substrate 11 (for example, at 135° and 315°).

In the present embodiment, the beam extraction voltage is changed bychanging the voltage to be applied to the first electrode. However, thebeam extraction voltage may be changed by another method. For example,the beam extraction voltage may be changed with the voltage applied tothe third electrode changed by applying a positive voltage lower thanthat for the first electrode to the third electrode. Instead, an energyof incidence of the ion beam onto a substrate may be changed by changinga voltage to be applied to the substrate holder.

Moreover, in the present embodiment, the grid 9 does not necessarilyinclude three electrodes. This is because an essential point of thepresent embodiment is to change the energy of the ion beam according tothe rotational phase of the substrate as described above.

Fifth Embodiment

An embodiment of the present invention can be combined with anotheretching method. An example is explained below in which the presentinvention is combined with reactive ion etching (RIE). As etching meansof RIE, there have been known an etching apparatus usingcapacitively-coupled plasma generated by parallel flat-plate electrodes,and an etching apparatus using inductively-coupled plasma generated byan antenna coil. An advantageous point of RIE is that the RIE does nothave limitation on the incident angle of ions unlike the IBE, andtherefore is capable of etching an object to be processed by attractingions into gaps between fine patterns. However, in the case of theforegoing structure including metal films, such as a TMR element forMRAM, physical etching of ions tends to be dominant over etching throughchemical reaction. Magnetic metals removed by physical etching aredifficult to volatize, and are redeposited onto the side walls of theTMR elements. For this reason, the RIE process on fine patterns is alsodifficult because the etching products remain on the bottom portions ofthe pattern trenches as in the conventional IBE process method.

If an IBE process according to an embodiment of the present invention isperformed after a RIE process, etching products redeposited on the sidewalls of the patterns by the RIE can be removed by means of the trimmingeffect or the bottom portions of the pattern trenches, which aredifficult to process, can be processed. Timing for switching between RIEand IBE can be known by performing end point detection using an emissionanalysis device configured to detect the wavelength of plasma light. Inthe case where different apparatuses are used for RIE and IBE, theapparatuses installed at different places may be used to process finepatterns by the IBE according to an embodiment of the present inventionafter performing the RIE process, or a common transportation path may beused to perform these processes without breaking vacuum.

Sixth Embodiment

By use of an embodiment of the present invention, fine patternsprocessed by another apparatus can be further trimmed with favorableuniformity. A density distribution of plasma can be changed by changingan electric current fed to the electromagnet 8 illustrated in FIG. 2.Specifically, the adjustment of the plasma density distribution uses asolenoid as the electromagnet 8, and the solenoid is installed so as tosurround the outer periphery of the bell jar as illustrated in FIG. 2.The solenoid is connected to a DC power supply, not illustrated. When acurrent is fed to the solenoid, the solenoid generates a magnetic fieldin accordance with Ampere's circuital law, and forms lines of magneticforce which may scatter electrons concentrically outward from the centerof the plasma generation unit. When a small current is fed to thesolenoid, the plasma density tends to be high at the center. As thevalue of the current fed to the solenoid is increased, the plasmadensity distribution is flattened with outward diffusion. Fine patternsprocessed by another apparatus are analyzed in terms of a film thicknessdistribution tendency in a substrate surface by using an atomic forcemicroscope, an optical measuring or scanning electron microscope, or thelike, and the current to be fed to the electromagnet 8 is adjusted basedon the analysis result. For example, let us consider the case where finepatterns processed by RIE have a large film thickness at a centerportion in a substrate, and have a small film thickness at an outerperipheral portion in the substrate. In this case, a current to be fedto the electromagnet is adjusted such that the plasma density at thecenter can be higher while the plasma density at the outer periphery canbe lower. Since the number of particles in the ion beam extracted by thegrid 9 is determined in proportion to the plasma density, the etch rateat the center portion with a high ion density is high. In this way,variations among fine patterns after process can be corrected bycombining the present invention with an etching process using anotheretching method. The electromagnet 8 illustrated in FIG. 2 is providedsolely. Instead, another electromagnet may be added to outside of theelectromagnet 8, and the plasma density may be adjusted by usinginteractions between the inner and outer electromagnets.

Seventh Embodiment

In an embodiment of the present invention, etching is performed whilechanging an incident angle. This etching enables removal of redepositedfilms from many directions, and an enhancement in the trimming effect.In the present embodiment, the substrate 11 mounted on the substrateholder is located with a tilt to the grid 9 so that the incident angleof the ion beam can be aligned with pattern trenches. In addition, thesubstrate is exposed to the ion beam while changing its tilt angle (forexample, the tilt angle is changed from 30° to 20°). By changing thetilt angle of the substrate, the incident angle of the ion beam ischanged, which makes it easier to trim the side walls of the patternsand the bottom portions of the trenches.

More detailed description is provided by using FIGS. 16A and 16B. FIG.16A illustrates a state where the ion beam is incident on the substrate11 with a predetermined tilt. In FIG. 16B, the exposure to the ion beamis performed in a direction more perpendicular to the substrate 11 thanthe ion beam in FIG. 16A. Such exposure to the ion beam in the moreperpendicular direction enables elements J to be etched at an angledifferent from that of the ion beam in FIG. 16A. More specifically, inthe present embodiment, the exposure to the ion beam is started whilethe substrate 11 is held at a first tilt angle (for example, the statein FIG. 16A). Then, after the substrate 11 makes a predetermined numberof rotations, the substrate is changed to be held at a second tilt anglethat is different from the first tilt angle (for example, the state inFIG. 6B), and the exposure to the ion beam is continuously performed.The number of tilt angles to be changed over is not limited to two, butmay be three or more.

Moreover, the exposure to the ion beam in the more perpendiculardirection is also performed such that the exposure dose to the ion beamfrom the extending directions of the pattern trenches can become largeras in the embodiments described above. This enables the side walls ofthe elements J to be efficiently exposed to the ion beam as illustratedin FIG. 16B. More specifically, in the state in FIG. 16A, the ion beamis incident in directions almost parallel to the side walls of theelements J, and the incidence in the directions perpendicular to theside walls of the elements J is restricted by the neighboring elements.On the other hand, in the state in FIG. 16B, the incident angle of theion beam is more perpendicular, and accordingly the incident dose of theion beam from the directions perpendicular to the side walls of theelements J can be increased. Moreover, by increasing the exposure doseto the ion beam from the extending directions of the pattern trenches,the incident dose of the ion beam from the directions perpendicular tothe side walls of the elements J can be made larger than the incidentdose of the ion beam from the other directions. As a result, efficienttrimming can be performed. The tilt of the substrate may be fixed duringa predetermined number of rotations, or may be switched over at shorterintervals by swinging the substrate.

Eighth Embodiment

The foregoing seventh embodiment presents the mode where the tilt angleof the substrate 11 to the grid 9 is changed after a fixed number ofrotations or more.

In contrast to this, in the present embodiment, the tilt angle of thesubstrate 11 to the grid 9 is changed along with the rotational speed ofthe substrate 11 in the first embodiment. The present embodiment isdescribed below in detail by using FIG. 19.

FIG. 19 presents how the rotational speed of the substrate 11 changesaccording to its rotational position. In addition, the tilt angle Φ ofthe substrate 11 to the grid 9 is changed within a range of 20° to 60°around a base angle of 40°. It is preferable that Φ become largest whenthe rotational speed of the substrate 11 becomes lowest, and becomesmallest when the rotational speed of the substrate 11 becomes highest.By taking such control, when the ion beam is incident along the patterntrenches on the substrate 11, the etching can efficiently removeredeposited films adhered to the side walls of the elements and thelike. On the other hand, when the incidence of the ion beam isdifficult, the ion beam is made incident at an angle closer to theperpendicular angle, and thereby the etching can be performed whilereducing the influence of the shadows of neighboring elements.

Ninth Embodiment

The second embodiment presents the case where the energy amount of theion beam incident on the substrate is changed in the form of the sinefunction by changing the rotation pause time in the form of the sinefunction relative to the phase of the substrate. In contrast to this, inthe present embodiment, the substrate rotation is paused only under thecondition that the grid 9 is located near to the extending directions ofthe pattern trenches.

FIG. 21 presents how the rotation pause time of the substrate 11 changesaccording to the rotational position. In the present embodiment, thesubstrate rotation is paused at predetermined rotational angles near tothe rotational angles 0°, 90°, 180°, and 270° at which the grid 9 islocated in the extending directions of the pattern trenches. Afterexposure to the ion beam for a fixed time period, the substrate rotationis started again. In a real situation, the side walls of TMR elementsafter element isolation have a certain tilt angle to the substrate andan ion beam to be incident on the substrate diverges. For this reason,even when the present embodiment is implemented, the redeposited filmson the side walls of the elements are exposed to the ion beam.

The pausing of the rotation of the substrate only when the grid 9 islocated in the extending directions of the pattern trenches may befurther combined with the changing of the exposure dose to the ion beamor the voltage for the ion beam as described in the third embodiment orthe fourth embodiment. In this case, the energy amount of the ion beamincident on the substrate is made large only when the grid 9 is locatedin the extending directions of the pattern trenches, and otherwise theenergy amount of the ion beam is made small.

Moreover, the present embodiment may be combined with the changing ofthe rotational speed as in the first embodiment, or may be combined withthe changing of the tilt angle of the substrate as described in theseventh embodiment or the eighth embodiment.

Further, the ion beam etching may be performed while slightly changingthe rotational phase of the substrate holder 10 while the grid 9 islocated near to the extending directions of the pattern trenches. Forexample, after the substrate rotation is stopped at each ofpredetermined rotational angles near to the rotational angles 0°, 90°,180°, and 270°, the substrate 11 may be exposed to the ion beam whilethe substrate holder 10 is oscillated in rotational angle within a rangeof ±10° of the predetermined rotational angle. Such processing withslight movements of the substrate holder 10 enables the surface of thesubstrate to be processed more uniformly.

The foregoing embodiments of the present invention can be alteredvariously without departing from the spirit of the present invention.

Besides the above-illustrated patterns in the rectangular parallelepipedshape which are arrayed with the long-side and short-side ends thereofaligned with each other such that the pattern trenches cross each otherat perpendicular angles, the foregoing embodiments are also applicableto a discrete track medium or a line-and-space form having a largeaspect ratio as illustrated in FIG. 14, or to a process surface of asubstrate in any form such as not only a sine wave form, but also arectangle wave form, a triangle wave form, and a trapezoid wave form asillustrated in FIG. 15.

In addition, the foregoing embodiments are also applicable to patternsin a rectangular parallelepiped shape which are arrayed with both endsthereof aligned with an oblique direction as illustrated in FIG. 20. Inthis case, the directions D along the pattern trenches cross each otherobliquely at certain angles other than the perpendicular angles. Theforegoing embodiments are usable not only on patterns in a rectangularparallelepiped shape, but also patterns in a cylindrical shape.

The embodiments of the present invention are usable in various fieldssuch as magnetic heads for HDD, magnetic recording media for HDD,magnetic sensors, thin film solar cells, light emission elements,piezoelectric elements, and wiring formation for semiconductor elementsin addition to the TMR elements for MRAM illustrated above.

The invention claimed is:
 1. An ion beam processing method of processinga substrate mounted on a substrate holder by using an ion beam extractedfrom a plasma source by a grid, the method comprising: in performing ionbeam etching on the substrate located with a tilt to the grid whilerotating the substrate in an in-plane direction thereof, performing ionbeam processing such that an etching amount of an ion beam incident froman extending direction of a pattern trench formed on the substrate ismade larger than an etching amount of an ion beam incident from anotherdirection, wherein a rotational speed of the substrate when the grid islocated on a side in the extending direction of the pattern trenchformed on the substrate is made lower than the rotational speed of thesubstrate when the grid is located on a side in a direction differentfrom the extending direction.
 2. An ion beam processing method ofprocessing a substrate mounted on a substrate holder by using an ionbeam extracted from a plasma source by a grid, the method comprising: inperforming ion beam etching on the substrate located with a tilt to thegrid while rotating the substrate in an in-plane direction thereof,performing ion beam processing such that an etching amount of an ionbeam incident from an extending direction of a pattern trench formed onthe substrate is made larger than an etching amount of an ion beamincident from another direction, wherein the rotating the substrateinvolves a repetition of a rotation of the substrate and a pause of therotation, and wherein a rotation pause time of the substrate when thegrid is located on a side in the extending direction of the patterntrench formed on the substrate is made longer than the rotation pausetime of the substrate when the grid is located on a side in a directiondifferent from the extending direction.
 3. An ion beam processing methodof processing a substrate mounted on a substrate holder by using an ionbeam extracted from a plasma source by a grid, the method comprising: inperforming ion beam etching on the substrate located with a tilt to thegrid while rotating the substrate in an in-plane direction thereof,performing ion beam processing such that an etching amount of an ionbeam incident from an extending direction of a pattern trench formed onthe substrate is made larger than an etching amount of an ion beamincident from another direction, wherein, by controlling a voltage to beapplied to the grid, energy of the ion beam when the grid is located ona side in the extending direction of the pattern trench formed on thesubstrate is made higher than the energy of the ion beam when the gridis located on a side in a direction different from the extendingdirection.
 4. An ion beam processing method of processing a substratemounted on a substrate holder by using an ion beam extracted from aplasma source by a grid, the method comprising: in performing ion beametching on the substrate located with a tilt to the grid while rotatingthe substrate in an in-plane direction thereof, performing ion beamprocessing such that an etching amount of an ion beam incident from anextending direction of a pattern trench formed on the substrate is madelarger than an etching amount of an ion beam incident from anotherdirection, wherein, by controlling electric power to be applied to theplasma source, an ion density in the ion beam when the grid is locatedon a side in the extending direction of the pattern trench formed on thesubstrate is made higher than the ion density in the ion beam when thegrid is located on a side in a direction different from the extendingdirection.
 5. The ion beam processing method according to claim 1,wherein, by controlling a voltage to be applied to the grid, energy ofthe ion beam when the grid is located on the side in the extendingdirection of the pattern trench formed on the substrate is made higherthan the energy of the ion beam when the grid is located on a side in adirection different from the extending direction.
 6. The ion beamprocessing method according to claim 1, wherein, by controlling electricpower to be applied to the plasma source, an ion density in the ion beamwhen the grid is located on the side in the extending direction of thepattern trench formed on the substrate is made higher than the iondensity in the ion beam when the grid is located on a side in adirection different from the extending direction.
 7. The ion beamprocessing method according to claim 2, wherein, by controlling avoltage to be applied to the grid, energy of the ion beam when the gridis located on the side in the extending direction of the pattern trenchformed on the substrate is made higher than the energy of the ion beamwhen the grid is located on a side in a direction different from theextending direction.
 8. The ion beam processing method according toclaim 2, wherein, by controlling electric power to be applied to theplasma source, an ion density in the ion beam when the grid is locatedon the side in the extending direction of the pattern trench formed onthe substrate is made higher than the ion density in the ion beam whenthe grid is located on a side in a direction different from theextending direction.
 9. The ion beam processing method according to anyone of claims 1-4 or 5-8, wherein a tilt angle of the substrate to thegrid formed when the ion beam is incident from the extending directionof the pattern trench formed on the substrate is made larger than thetilt angle of the substrate to the grid formed when the ion beam isincident from another direction.